Abstract: Large steam turbine generators are expensive and have complex structures. Once damaged, they not only require a long maintenance cycle but also bring huge economic losses. The fault diagnosis and handling of the generator rotor, as an electromechanical high-speed rotating body, has always been a key and difficult point in the industry. This article introduces the overall structure, design philosophy, and key technologies of a novel online monitoring system for generator rotors. This system plays an important role in online monitoring and fault diagnosis of generator rotor operation status. The simulation test shows that the device operates safely and reliably, with excellent performance. In order to monitor the overall health of the generator rotor and main shaft of a 1000MW nuclear power unit, a rotor integrated monitoring system needs to be set, including rotor grounding monitoring, rotor temperature monitoring, Shaft voltage monitoring, shaft grounding monitoring and wet current monitoring. This system is of great significance for detecting early rotor faults, preventing unit accidents, and improving the reliability of generator unit operation.